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SSB and Demodulation

SSB and Demodulation. Analog and Digital Communications Autumn 2005-2006. USB. LSB. LSB. USB. Islands are not symmetric around. SSB-AM. First consider DSB-SC. Pass it through an “SSB filter”. (Transmission BW is twice the signal BW). SSB and DSB Comparison. For DSB:. For SSB:.

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SSB and Demodulation

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  1. SSB and Demodulation Analog and Digital Communications Autumn 2005-2006 CS477: Analog and Digital Communications

  2. USB LSB LSB USB Islands are not symmetric around SSB-AM First consider DSB-SC Pass it through an “SSB filter” CS477: Analog and Digital Communications

  3. (Transmission BW is twice the signal BW) SSB and DSB Comparison For DSB: For SSB: CS477: Analog and Digital Communications

  4. Information signal is Tone Modulation: SSB & DSB For DSB-SC or DSB: For USSB: For LSSB: CS477: Analog and Digital Communications

  5. Will Envelope detection work for SSB with tone modulation? NO, because envelope is a constant proportional to Tone Modulation For DSB-SC or DSB: For USSB: CS477: Analog and Digital Communications

  6. DSB Input SSB Filter SSB Output SSB With Arbitrary Input Assume SSB filter as a bandpass system with DSB as the input signal Then, apply equivalent lowpass analysis CS477: Analog and Digital Communications

  7. What is ? SSB With Arbitrary Input (Start from a DSB signal) CS477: Analog and Digital Communications

  8. (For USSB) SSB With Arbitrary Input For USSB Filtering: (we are filtering the DSB input signal) CS477: Analog and Digital Communications

  9. (For LSSB) SSB With Arbitrary Input Similarly, For LSSB: In general, for LSSB and USSB: Thus we can find the lowpass output CS477: Analog and Digital Communications

  10. SSB With Arbitrary Input Using the transform pair: Thus, lowpass output in time domain is: What is the SSB output from SSB filter? CS477: Analog and Digital Communications

  11. SSB With Arbitrary Input SSB output is a bandpass signal What are the in-phase and quadrature components? What is SSB envelope? CS477: Analog and Digital Communications

  12. DSB Input SSB Filter SSB Output SSB Generation • Perfect SSB filters • Hard to realize • Rely on the absence of spectral components at low frequencies • Use of phase shift methods CS477: Analog and Digital Communications

  13. VSB Signals • Used in commercial TV broadcast • Include a low power carrier in transmission • One sideband is passed completely and the other is passed partially • Generated by using a VSB filter • Anti-symmetric around the carrier frequency • Has amplitude 0.5 at the carrier frequency CS477: Analog and Digital Communications

  14. Demodulation • Frequency conversion • Synchronous detection • Requires tight synchronization at the receiver • Envelope detection • Can be used with modulations where envelope truly reflects the information signal • Can not be used if envelope is distorted CS477: Analog and Digital Communications

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